text: The pressure in the flow is reduced at the edge of the can spout. However, since the air pressure on the outside of the flow is the same everywhere, there is a pressure difference that pushes the liquid to the edge. Depending on the materials used, the outside of the spout is now wetted during the flow process. At this point, additional interfacial forces occur : the liquid runs as a narrow trickle along the spout and can until it detaches from the underside.
  The unwanted teapot effect only occurs when pouring slowly and carefully. In fast pouring, the liquid flows out of the spout in an arc without dripping, so it is given a relatively high velocity with which the liquid moves away from the edge (see Torricelli outflow velocity). The pressure difference resulting from the Bernoulli equation is then not sufficient to influence the flow to such an extent that the liquid is pushed around the edge of the spout.
  Since the flow conditions can be described mathematically, a critical outflow velocity is also defined. If it falls below when pouring, the liquid flows down the pot; it drips. Theoretically, this speed could be precisely calculated for a specific can geometry, the current air pressure and the fill level of the can, the spout material, the viscosity of the liquid and the pouring angle. Since, apart from the fill level, most of the influencing variables cannot be changed (at least not sufficiently precisely in practice), the only way to avoid the teapot effect is usually to choose a suitable geometry for the pot.
  Another phenomenon is the reduction in air pressure between the spout and the jet of liquid due to the entrainment of gas molecules (one-sided water jet pumping effect), so that the air pressure on the opposite side would push the jet of liquid to the spout side. However, under the conditions usually prevailing when pouring tea, this effect will hardly appear.